Michael Chase and Kelly Landen also found out that from 1999 to the present the running average for total species decline is about 61%.
It appears unclear what exactly is causing the catastrophic decline, but it seems that the shrinking numbers of wildlife in the Okavango Delta is a result of "a complex mixture of local causes", including human encroachment, game fences and poaching. Another factor could be fire. Much of the area surveyed in the late dry season of 2010 was burning.